Car info : 87 t2 s5 turbo and exhaust 3 inch back no muff no emissions , has bac efan wired to relay using control fan positive as pin . tbm greddy type s bov

My 87 t2 is now back together . It starts very easily but hangs around 1200- 1500 then shoots to 3k stays there for a little then climbs to 4k gradually .It then acts like it is going to stall but catches around 800 and goes back to 3k if you touch the pedal. Any Ideas ?

 

Vacuum Leak (did you use replacement seals on the block off plates)?

TPS adjusted?

Throttle Cable & Stop Screw adjusted?

Timing Set Correctly?

 

Timing is good
Seals good
im adjusting tps atm
im wondering about the few vaccum lines i have left , they dont leak and they are back where they came from , Yet where they in the right spot . its hard to find a vaccum diagram , not because ofthere arent any available just cause everyone you find is different from the ones seen previous.
One thing I'm wondering about is the omp setup. my linkage was bent and not opening the accuator on the pump , so i removed the linkage and premixed with everything intact.
Ill post more findings if I get them

 

do you still have the rats nest? if not then you only need like 2 vacuum lines. makes life a lot better without it.

not sure if it makes a difference but do you still have the OMP hooked up? minus the linkage

 

The tps is in spec and the prob persists. Yes the omp is intact with new hoses too just not being actuated by tb. When it gets up to temp it only bounces between 500 and 2k and runs well other than insane surging. I chose to modify the nest and remove unused lines from it. I also kept the prcv line intact so I have 3 vacuum lines .

 

And what happens if the BAC is unplugged or is it nonexistant? And this problem persists when the engine is warmed up as well? And can you verify that the throttle linkage is moving or not during the bouncing?

 

if the bac is unpluged or cross wired it runs worse 3k-4k and gets stuck no throttle response below 3k. The linkage isnt moving during the surging while hot , when its cold i have to keep it running so i m not sure. still no improvements though .

 

Not sure about this but if the idle is surging while the throttle linkage is stationary and the throttle plates essentially closed then the problem seems to be a function of unmetered air. I suppose you could via the use of your fingers or needle nosed pliers squeeze the hoses that do exist on your setup to see if there are any noticeable changes as the idle is pulsating.

 

You can check for vac leaks using a can of starting fluid or WD40. If the idle picks up and smooths out when you spray over a rubber hose, that's where the leak is.

 

today after heating up i sat there with the clutch in and it bounces between 1.3-1.6 k . I figured id try unpluggin the bac , and no difference the erratic idle didnt rise or lower just stayed the same . Ill try pinching lines in the morning and post my vacuum diagram and see if maybe I crossed something, beyond surging the car runs well. There is however some lag in the pedal ., only when under 3k thou.

 

If by chance the BAC was stuck in the open position then unplugging it would make for no change. Closing the hose to the throttle body should be another item to look at.